Is Your Dam a "Dam With a Safety Risk"? The Dam Safety Regulations Explained

A dam is a “dam with a safety risk” under section 117 of the National Water Act if it can hold more than 50 000 m³ and has a wall more than 5 m high, or if the Minister declares it one. The owner must register it, the Department of Water and Sanitation (DWS) classifies it into Category I, II or III, and the category decides who must design it, what manuals it needs, and how often its safety must be evaluated. The Dam Safety Regulations (GN R139 of 24 February 2012) set out the detail.

Need the flood hydrology, spillway hydraulics or dam break inundation maps for a dam safety evaluation? We provide the hydrology and hydraulics the approved professional person relies on.

Dam safety evaluations

When a dam has a safety risk

Section 117 defines a dam with a safety risk as any dam that:

• “can contain, store or dam more than 50 000 cubic metres of water, whether that water contains any substance or not”; and
• “has a wall of a vertical height of more than five metres”, measured “between the lowest downstream ground elevation on the outside of the dam wall and the non-overspill crest level or the general top level”.

Both conditions must be met. A farm dam holding 80 000 m³ behind a 4 m wall is not automatically one, and neither is a 7 m wall holding 30 000 m³. But section 118 lets the Minister declare a category of dams, or an individual dam, to be a dam with a safety risk regardless of size, and direct the owner to obtain a report on its safety by an approved professional person.

The words “whether that water contains any substance or not” bring in pollution control dams and evaporation ponds. The regulations define storage capacity separately for “any residue deposit including tailings dams”, so tailings dams that meet the test are covered too.

Registration

The owner must register the dam (section 120). The application is due “within 120 days” of the dam becoming able to hold water, or of the Minister’s declaration.

In November 2024 DWS published a notice (GN 5576, Gazette 51637) calling on owners of unregistered dams with a safety risk “to register their dam(s) at the Department within 60 days”, and on owners of registered dams to confirm their details. It uses forms DW692E (classification) and DW693E (registration of an existing dam), states that no charge is payable, and warns of a fine or imprisonment of up to five years for failing to register. The 60 days was a one-off window for existing dams; the 120-day rule still applies to new ones.

Classification: size, hazard and category

DWS classifies each dam with a safety risk, notifies the owner, and may revise the classification later (regulation 2). For a proposed dam, the owner submits the classification information once the feasibility studies are done.

Size depends on the maximum wall height:

Size class	Wall height
Small	Less than 12 m
Medium	12 m or more, but less than 30 m
Large	30 m or more

Hazard potential depends on what would happen if the dam failed:

Hazard potential	Potential loss of life	Potential economic loss	Potential impact on resource quality
Low	None	Minimal	Low
Significant	Not more than ten	Significant	Significant
High	More than ten	Great	Severe

The highest of the three governs. A dam holding polluted water is rated at least significant for resource quality, and one holding hazardous substances, severe.

Category combines the two:

Size	Low hazard	Significant hazard	High hazard
Small	Category I	Category II	Category II
Medium	Category II	Category II	Category III
Large	Category III	Category III	Category III

Hazard potential is where downstream development matters. A small dam whose failure would flood only farmland may be low hazard. Once houses are built in the area a failure would flood, the same dam can be significant or high hazard, which makes it Category II. A dam break analysis is how that area is mapped.

What each category needs

	Category I	Category II	Category III
Design	A design report complying with “acceptable dam engineering practices” for a licence to construct; the regulations do not name an approved professional person	An approved professional person designs the dam	An approved professional person, assisted by a professional team
Licence to impound water	Not required	Required, with an operation and maintenance manual and emergency preparedness plan	As for Category II
Dam safety evaluation	When DWS requests one, at intervals of five to ten years	Within three years of completion, then at intervals of not more than five years (DWS may extend to ten)	As for Category II, by an approved professional person with a professional team, plus a risk analysis if DWS requests it

For Category II and III dams, the owner must appoint an approved professional person to compile an operation and maintenance manual and an emergency preparedness plan, and keep both up to date (regulation 32). For Category III, that person works with a professional team.

An approved professional person is an engineer registered with the Engineering Council of South Africa and approved by the Minister after consultation with the Council. Section 119 gives that person “a duty of care towards the State and the general public”, not only to the dam owner.

The emergency preparedness plan and inundation maps

Regulation 28 sets out what the emergency preparedness plan contains. It includes:

• “inundation maps delineating areas downstream of the dam that would be flooded as a result of a dam failure”, and, where the approved professional person considers it necessary, areas flooded by selected natural floods;
• a notification flowchart showing “who is to be notified, by whom, and in what priority”;
• historical flood marks in built-up areas.

The regulations note that this plan “is not an emergency evacuation plan”. It gives disaster management authorities the information they need to prepare one.

Where the hydrology comes in

Most of the engineering in a dam safety evaluation depends on flood estimates and hydraulics:

• Design floods for the spillway, including the extreme floods the dam must survive. Our post on PMF vs RMF explains which applies.
• Spillway and freeboard checks against those floods.
• Dam break modelling for the inundation maps and the hazard classification.

For mine dirty water dams, GN 704 also sets a 0.8 m minimum freeboard and 1:50-year spill rules, unless Chapter 12 specifies otherwise. See GN 704 regulation 4.

See our dam safety evaluations, dam break analysis and PMF analysis services, or send us the dam’s details.

This post explains the documents listed below. It is not legal advice; requirements change and are applied case by case, so confirm them with the relevant authority before relying on them.